InwardRectifierKanäle

Inward rectifier potassium channels, often abbreviated as GIRKs or Kir channels, are a superfamily of ion channels found in the plasma membranes of many cell types. These channels selectively conduct potassium ions (K+) into the cell, particularly when the membrane potential is more negative than the potassium equilibrium potential. Conversely, their conductance of potassium ions out of the cell is significantly reduced at more positive membrane potentials. This characteristic rectification property gives them their name.

The function of Kir channels is crucial for regulating cell excitability and membrane potential. In neurons, they play a role in setting the resting membrane potential and dampening excessive neuronal firing. In cardiac cells, their activity is vital for maintaining the repolarization phase of the action potential and influencing heart rate. In other tissues, such as pancreatic beta cells, they are involved in regulating insulin secretion.

Kir channels are a diverse group, with several distinct subfamilies (e.g., Kir1.x to Kir7.x) that differ in their physiological roles, subunit composition, and regulatory mechanisms. They are typically tetramers, meaning four protein subunits assemble to form a functional channel pore. These subunits can be homomeric (composed of identical subunits) or heteromeric (composed of different subunits), leading to a wide range of functional properties. Regulation of Kir channel activity can occur through various means, including changes in intracellular ion concentrations (like K+ and ATP), G protein signaling, and interaction with other cellular proteins. Mutations in genes encoding Kir channels have been linked to various human diseases, including certain types of epilepsy, cardiac arrhythmias, and Bartter syndrome.